The letter was sent in advance of a meeting scheduled tomorrow morning, at which the Commission on Chicago Landmarks is scheduled to consider the proposal.

The letter was obtained from a source close to the proposed development.

"I am very pleased that we have been able to condense a very lengthy list of community concerns down to a handful of items," Mr. Tunney wrote. But, "as I have consistently represented, only until the following changes are made will I support the Cubs' application" before the landmarks group and the Chicago Plan Commission.

Specifically, to get his support, Mr. Tunney said the plan must be amended to reduce the size of a left-field Jumbotron, from 6,000 square feet to 3,500 square feet. Also similarly pared must be the right-field advertising sign, from 1,000 square feet to 600 square feet.

The North Side alderman also said the pedestrian bridge must go. Also out: a patio/outdoor deck bridging Patterson Street. And the hotel's lobby must be moved from Patterson to either the Addison Street or Clark Street side, he said.

Mr. Tunney also complained that the proposal — derived from a "framework" unveiled in an April 14 statement from him, the team and Mayor Rahm Emanuel — is being rushed. The formal paper application was submitted May 1.

"I will expect a greater level of responsiveness and consideration from you and the Cubs organization as we finalize (approval)," he concluded. "We will continue to work with you to refine minor elements."

I suspect the Cubs will not consider the demand to cut the size of that moneymaking Jumbotron to be "minor." Asked for a reaction, a team spokesman said only, "We look forward to continuing to work with the city and landmarks commission."

Best translation of that: The ball now is in the hands of Mr. Emanuel. In a statement that doesn't say a lot, the mayor's office said, "All sides continue to work together to modernize Wrigley Field and invest in the surrounding neighborhood. We have made a great deal of progress in a short amount of time. Tomorrow, we will continue to move forward on a number of major items at the landmarks commission meeting."

Mr. Tunney's office said he was gone for the day and not reachable.

By tradition, zoning proposals like this require the approval of the local alderman to get through the City Council — unless, of course, the mayor's on the other side.